Food production on ever-dwindling agricultural land is a severe problem in Ethiopia, necessitating the adoption of more efficient and sustainable land-use strategies to feed the country's growing population. The benefits of intercropping are known to be limited by a variety of factors such as companion crop sowing date and variety. The present study was therefore initiated to evaluate the effect of varieties and planting dates of lupines in bread wheat-lupine under an additive design intercropping system in Northwest Ethiopia. Field experiments were conducted for two years in Adet and Debre Tabor experimental sites. The treatments consisted of four planting dates of lupines and two varieties of lupine. Moreover, the sole crop of bread wheat (Triticum aestivume L.), local lupine (Lupinus albus L.) and sweet lupine (Lupinus angustiflolius L.) were also included. The experiments were laid out in factorial randomized complete block design (RCBD) with three replications. The results showed that at the Adet experimental site, the highest land equivalent ratio (LER) was recorded in the simultaneous planting of sweet lupine and bread wheat (1.3), followed by the planting of sweet lupine two weeks after bread wheat (1.23). While at Debre Tabor experimental site, the highest LER was recorded in planting sweet lupine two weeks after bread wheat (1.67). A greater area time equivalent ratio (ATER) was reported in the simultaneous planting of sweet lupine and bread wheat (1.29), followed by the planting of sweet lupine after bread wheat (1.22) at the Adet experimental site. A greater ATER was also recorded in the planting of sweet lupine after bread wheat (1.53) had the highest ATER in Debre Tabor, followed by simultaneous planting of sweet lupine after bread wheat (1.39) intercropping. This revealed that sole cropping would necessitate 29 and 53% more area, respectively, to attain the same yield as intercropping. In Adet, the simultaneous planting of sweet lupine and bread wheat intercropping, while in Debre Tabor, planting of sweet lupine two weeks after bread wheat boosted productivity, and production efficiency and is a viable option for increasing household food security.

Land equivalent ratio (LER) is a most widely used indicator of yield advantage of multi-crop farms over sole-crop farms, and usually measured using crop biomass yield per unit area. Most often, crop yields are compared between both systems using the same area. In this paper, we demonstrate that although the yield per unit area and the yield per plant are widely different, LER remains invariant. As a corollary, area time equivalent ratio and land use efficiency, derived from LER, also remain unchanged when using the two different measures of crop yields. We recommend that when the estimation of the exact land area is difficult due to complex crop planting designs, yield per plant estimate is much easier and equally valid for estimation of LER and its derivative indices.

Strip intercropping seeks to capture the biological efficiency of intercropping in traditional agricultural systems and is compatible with agricultural equipment used in the U.S. This efficiency stems from complementary use of resources by constituent crops and is a function of crop selection, strip width and orientation, weed control, and other factors. Strip intercropping requires a high level of management; further, some reports suggest the gains and losses more-or-less balance in actual production situations. These questions are best addressed by the performance of strip intercropping as implemented by farmers in production situations.

Practical Farmers of Iowa (PFI) members have worked with Iowa State University agronomists to evaluate strip intercropping. For three years six farmers compared strip intercropping to field blocks of individual crops. The strip intercrop systems employed three crops: corn, soybeans, and small grains with a forage legume underseeding. The comparison systems, crops grown in sole-crop blocks, consisted of the same three crops on four farms (planting pattern comparison) or, on two farms, just corn and soybeans in rotation (systems comparison). Yields and field operations were recorded and entered in the Iowa State University Crop Enterprise Record System (CER) to derive gross profit, total production cost, and net profit for each crop component and for each cropping system on every farm. Strip intercropping net profit was generally greater than that in field blocks, and intercropping compared favorably with CER results obtained from corn-soybean rotations on other farms around Iowa. Land equivalent ratios (LER) were usually greater than 1.0, indicating satisfactory biological efficiency. Despite occasional problems, in this set of 18 site-years strip intercropping was associated with greater stability of net profit.